The protein responsible for neoplastic conversion of cells by avian sarcoma viruses (ASV) is a 60,000 dalton phosphoprotein encoded by the viral src gene and designated pp60src. This protein appears to be a cyclic AMP-independent protein kinase, suggesting that aberrant phosphorylation of cellular proteins by pp60src may be involved in the mechanism of cellular transformation by ASV. I plan to study the structural and functional characteristics of the src protein in the hope of establishing correlations between the physical state of the src protein and phenotypic changes in cells. Specifically, the central goals of this project will be: to identify different structural and/or functional forms of the viral transforming protein; to purify and compare to pp60src, a normal cellular protein (designated pp60sarc) that is antigenically, structurally, and functionally very similar to the viral transforming protein; and to examine the expression, at the protein level, of the wild-type and in vitro mutagenized viral src gene that has been introduced into bacteria and vertebrate cells in culture. I will employ: polyacrylamide and agarose gel electrophoresis; immunoprecipitation and immunoaffinity techniques; biochemical fractionation schemes; proteolytic peptide and phosphoamino acid analyses; recombinant DNA-mediated methodologies; and DNA-mediated transfer procedures to gain such information.